You MUST get the tumbler to the #1 position else face a difficult and expensive drill-out process. I'd advise squirting some lubrication into the keyhole and using the vibrating sander along with gentle wiggling of the key for as long as it takes to get the key to turn. Consider buying a new key from your local dealer, if the existing key is not in like-new condition.

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970